using System;
using System.Collections.Generic;
using System.Threading.Tasks;

namespace Parse.Common.Internal
{
    /// <summary>
    /// An abstraction for accessing persistent storage in the Parse SDK.
    /// </summary>
    public interface IStorageController
    {
        /// <summary>
        /// Load the contents of this storage controller asynchronously.
        /// </summary>
        /// <returns></returns>
        Task<IStorageDictionary<string, object>> LoadAsync();

        /// <summary>
        /// Overwrites the contents of this storage controller asynchronously.
        /// </summary>
        /// <param name="contents"></param>
        /// <returns></returns>
        Task<IStorageDictionary<string, object>> SaveAsync(IDictionary<string, object> contents);
    }

    /// <summary>
    /// An interface for a dictionary that is persisted to disk asynchronously.
    /// </summary>
    /// <typeparam name="TKey">They key type of the dictionary.</typeparam>
    /// <typeparam name="TValue">The value type of the dictionary.</typeparam>
    public interface IStorageDictionary<TKey, TValue> : IEnumerable<KeyValuePair<TKey, TValue>>
    {
        int Count { get; }
        TValue this[TKey key] { get; }

        IEnumerable<TKey> Keys { get; }
        IEnumerable<TValue> Values { get; }

        bool ContainsKey(TKey key);
        bool TryGetValue(TKey key, out TValue value);

        /// <summary>
        /// Adds a key to this dictionary, and saves it asynchronously.
        /// </summary>
        /// <param name="key">The key to insert.</param>
        /// <param name="value">The value to insert.</param>
        /// <returns></returns>
        Task AddAsync(TKey key, TValue value);

        /// <summary>
        /// Removes a key from this dictionary, and saves it asynchronously.
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        Task RemoveAsync(TKey key);
    }
}